On Thu, Apr 21, 2022 at 1:15 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > Looks good, and is easy to backport; thanks. > > However, once we have also your series "KVM: X86/MMU: Use one-off > special shadow page for special roots", perhaps the passthrough sp can > be converted to a special root (but now with a shadow_page) as well? > It will be much more complicated. The current code allows fast_pgd_switch() for shadowing 5-level NPT for 4-level NPT L1 guests because both the host and the guest are 64 bit. Using a special shadow page will disallow fast_pgd_switch(). And it will make using_special_root_page() more complicated. It will require a different kind of special shadow page to make it able to do fast switch.
